| As an important human physiological parameter, blood pressure can reflect the functional status of the human heart and blood vessels, the clinical diagnosis of the disease, observed an important basis for treatment. Blood pressure is the lateral earth pressure per unit area of vessel wall when blood flow in blood vessels, is an important parameter to reflect the function of the human circulatory system, the heart pumping function, heart rate, peripheral vascular resistance, aortic and large artery elasticity, the body blood volume and the physical state of blood and other factors are reflected in the blood pressure indicators. Blood pressure have an important role in the detection of disease prevention and treatment, the clinical need of critically ill patients and surgical patients to implement the continuous custody of the blood pressure, so that health care workers can take timely rescue measures when patients are unexpected. Blood pressure monitoring in home health care and the clinical diagnosis is very important.At present, the blood pressure measurement methods can be divided into two major categories of direct measurement and indirect measurement. The direct measurement method is to connect the pressure sensor catheter directly into the aorta or ventricular to detect blood pressure signal, capable of continuous measurement. Since this method directly measured blood pressure data is the most accurate, so it is seen internationally as the gold standard for blood pressure monitoring. But it need high technical requirements, and traumatic, generally restricted to critically ill patients. The indirect measurement method is obtained indirectly through the detection of arterial wall pulsatility, vascular volume changes in parameters of blood pressure, user-friendly and been widely used clinically.Operability problems are prevalent in the traditional blood pressure monitoring technology, and human blood pressure with the physiological cycle, personal feelings, the outside world and the inherent variety of stimuli change, with significant volatility. This dissertation presents a photoplethysmography-based non-invasive continuous blood pressure measurement, it can effectively overcome the shortcomings of traditional methods and has a great advantage for blood pressure monitoring in clinical care and special circumstances, in dissertation, and this method was studied.In this dissertation, the work done by including the following aspects: 1. Lambert-Beer law reflects the law of the optical absorption, the absorbance of the material at a certain wavelength, it is proportional to the concentration. Based on the Lambert-Beer law and the detection principle of the photoelectric sensor, we can establish connection between the transmitted light intensity and photoelectric sensor output voltage, establish connection between the Lambert Beer law and human arterial blood pressure, deduce the specific expression of human systolic and diastolic blood pressures, and create a non-invasive blood pressure measurement model.2. According to the non-invasive blood pressure monitoring model has been established, design the hardware circuit of noninvasive blood pressure monitoring, including optical data acquisition circuit, the primary amplifier, low pass filter circuit, after stage amplifier, A/D converter circuit and serial output circuit.3. According to the non-invasive blood pressure monitoring model has been established, design the software program of non-invasive blood pressure monitoring. The microcontroller program written using Keil uVision2procedures, and written into the AT89C51chip; PC program uses VB6.0to write, using the MSComm control to the serial communication.4. According to non-invasive blood pressure measurement model has been established, complete the experiment. Contrast the measured blood pressure values to non-invasive blood pressure measurement methods with the traditional method, verify the validity and accuracy of noninvasive blood pressure measurement methods. |
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